(i) Technical Field
The present invention relates to an image forming apparatus.
(ii) Related Art
In electrophotographic image forming apparatuses, a two-component developer (in which toner and magnetic carriers are mixed) or a magnetic one-component developer (in which magnetic toner is the principal component) is often used. The developer is transported to a developing roller (an exemplary developing unit) by a transporting member from a developer containing section of a developing device, and is then transported to a position (a development nip where a development pole of the developing roller is positioned) opposing a photoconductor drum (an exemplary image carrier) while being magnetically attracted to a peripheral surface of the developing roller. Then, the developer is transferred to the photoconductor drum, so that an electrostatic latent image that is formed on the photoconductor drum is developed.
In image forming apparatuses having such a structure, when the developing roller is one that rotates in a direction opposite to the direction of rotation of the photoconductor drum at a portion of the developing roller opposing the photoconductor drum, a suction duct (an exemplary developer sucking section) that is open above the developing roller is provided, so that developer (cloud toner) that is scattered without being supplied for development is sucked using negative pressure.
Therefore, when the sucked cloud toner passes the suction duct, a portion of the cloud toner adheres to/accumulates on an inner wall of the duct. When the suction duct is oriented downward, the accumulated toner sporadically drops onto the developing roller. When the developing roller rotates in the direction that is mentioned above, a transport pole of the developing roller causes the dropped toner to be transported into the developing device and to be collected.
Here, as the amount of cloud toner that is generated is increased, the amount of toner that drops at the same time is increased, as a result of which the toner transport capability of the developing roller is exceeded. Therefore, the toner reaches and passes the development nip. The toner that has passed the development nip is thinly scattered in the vicinity of the toner that has been transferred to the photoconductor drum. The thinly scattered toner causes a partial increase in toner density, and reduces image quality.
In order to prevent such a phenomenon, it is necessary to increase the toner transport/collecting capability of the developing roller so that the dropped toner does not reach the development nip. In order to achieve this, the toner drop position may be situated further downstream of the transport pole. However, when an end of the suction duct is moved away from the transport pole by using such a structure, the cloud toner that is generated at the transport pole is also sucked by the suction duct.